East Pacific/2015/01C/Archive/1
Public Advisory TROPICAL DEPRESSION ONE-C SPECIAL PUBLIC ADVISORY NUMBER 1 WIKI-HURRICANES FORECASTING CENTER 8:00 AM HST TUE JUL 7 2015 ...FIRST CENTRAL PACIFIC TROPICAL DEPRESSION FORMS WELL SOUTHWEST OF HAWAII... SUMMARY OF 8:00 AM HST...18:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...8.0N 166.6W CENTER POSITION CONFIDENCE: MEDIUM ABOUT 1,080 MI...1,740 KM SSW OF HONOLULU, HAWAII MAXIMUM SUSTAINED WINDS...30 KT...35 MPH...55 KM/H MINIMUM BAROMETRIC PRESSURE...1006 MB...29.71 INCHES PRESENT MOVEMENT...NNW AT 6 KT...7 MPH...11 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 8:00 am HST, the center of newly-formed Tropical Depression One-C was located with high confidence near 8.0N 166.6W, about 1,080 miles (1,740 km) south-southwest of Honolulu, Hawaii. Maximum sustained winds were 30 knots (35 mph, 55 km/h), the minimum barometric pressure was 1006 millibars (29.71 inHg), and the cyclone was moving north-northwest at 6 knots (7 mph, 11 km/h). Environmental conditions are expected to be generally favorable for slow development over the subsequent 48 hours. NEXT ADVISORY ------------------- Next complete advisory at 11:00 am HST. $$ Forecaster TAWX14 Discussion TROPICAL DEPRESSION ONE-C SPECIAL DISCUSSION NUMBER 1 WIKI-HURRICANES FORECASTING CENTER 8:00 AM HST TUE JUL 7 2015 The area of disturbed weather well southwest of the Hawaiian Islands has organized sufficiently to be declared a tropical depression. Satellite animations indicate that, while the extent of deep convection has decreased throughout the past few hours, spiral bands have become much more distinct, especially across the southern semicircle. Upper-level outflow has expanded in all quadrants except the northeast. On the basis of an earlier ASCAT pass, the initial intensity has been set at 30kt, making One-C the first depression within the Central Pacific this year. Environmental conditions appear conducive for strengthening throughout the forecast period. Wind shear, although a high 15 to 20 knots at the current time, is expected to fall below 10 knots by 36 hours. Sea surface temperatures are expected to range between 28-29C past day 5. Mid-level relative humidity values are expected to remain generally above 65% throughout the period. Despite this, there is little consensus between global and hurricane models regarding the forecast intensity of One-C. The GFS shows little to no change in intensity over the next 5 days, maintaining the cyclone as a borderline tropical storm. The ECMWF shows slow intensification to strong tropical storm strength by 120 hours, with rapid intensification into a Category 3 hurricane shortly outside the period. The SHIPS and LGEM both indicate steady strengthening over the coming days, with 120 hours intensities at 75kt and 92kt, respectively. Examining various products from the GFS, I see little reason why the model is being so conservative with regard to intensity. As such, the forecast leans closer to an ECMWF/SHIPS/LGEM blend. One-C is expected to be near hurricane intensity at the end of the period. The cyclone is moving slowly north-northwestward this morning. This motion is being imparted due to a mid-level disturbance in the vicinity of the Hawaiian Islands acting to create a weakness in the subtropical ridge to One-C's north. Over the coming days, this mid-level ridge is expected to re-intensify, which should force the tropical depression on a more west-northwest track. The GFS and ECMWF are in good agreement with one another, and the track forecast closely follows a blend of those two models. INIT 07/1800Z 8.0N 166.6W 30 KT 35 MPH 12H 08/0000Z 8.4N 167.0W 30 KT 35 MPH 24H 08/1200Z 9.2N 167.7W 35 KT 40 MPH 36H 09/0000Z 9.9N 168.3W 40 KT 45 MPH 48H 09/1200Z 10.3N 169.0W 45 KT 50 MPH 72H 10/1200Z 10.7N 170.7W 50 KT 60 MPH 96H 11/1200Z 11.6N 173.1W 55 KT 65 MPH 120H 12/1200Z 13.3N 176.5W 65 KT 75 MPH $$ Forecaster TAWX14